focus- the place in the earth where stress releases epicenter- the place above the focus seismic waves- the thing that carries energy caused by an earthquake primary waves- waves that diverge and squeeze rock secondary waves- waves that move up and down surface waves- come after p and s waves, but are mare destructive than both seismograph- senses vibrations in the earth magnitude- the analysis of the energy released, mostly waves along the cracks in the earth mercalli scale- a scale made to measure the strength of the earthquake ritcher scale- a scale made to rate the waves measured by another type of tool movement magnitude scale- a tool that guesses the complete power used in a quake
Outline
Seismic waves
Seismic waves
causes vibrations when stress is released
that point is the focus, above is the epicenter
vibrations cause earthquakes
move like ripples in a pond
vibrations/earthquake is strongest at the epicenter
three types of seismic waves, P waves, S waves, surface waves
Primary Waves (P waves)
compress and expands ground
particles of the crust vibrate forward and back along the path of the wave
Secondary Waves (S waves)
moves ground up and down, and side to side
shakes back and forth
shakes structures hard
cannot shake liquid
Surface waves
move more slowly, but make the strongest movements in the ground
come slower than P or S waves
Shakes buildings from side to side
some P and S waves are transformed into surface waves
Detecting Seismic waves
seismograph
tool for recording earthquakes
detects ground movements, needle with pen on it shakes and writes the vibrations
we use electronic ones now
Measuring Earthquakes
Magnitude
system that measures the strength of an earthquake
three main ways of measuring earthquakes: Mercalli scale, Richter scale, and the moment magnitude scale
Mercalli scale
measures quake on its intensity in one place
tells how it affects the land
Richter scale
recorded by special seismograph
used for about 50 years
accurate for smaller, nearby quakes
Moment Magnitude Scale
finds amount of energy released at focus
can tell earthquakes near or far
also uses electronic seismograph
Locating the Epicenter
Seismic waves timings
P waves, then S, than a while later Surface waves
to find the epicenter scientists find the difference between the arrival time of the P and S waves
more split apart the two timings are the farther the epicenter
creates three circles, in middle of each there is a seismograph, where circles meet is the epicenter
Table of Contents
Measuring Earthquakes
Vocabulary
focus- the place in the earth where stress releases
epicenter- the place above the focus
seismic waves- the thing that carries energy caused by an earthquake
primary waves- waves that diverge and squeeze rock
secondary waves- waves that move up and down
surface waves- come after p and s waves, but are mare destructive than both
seismograph- senses vibrations in the earth
magnitude- the analysis of the energy released, mostly waves along the cracks in the earth
mercalli scale- a scale made to measure the strength of the earthquake
ritcher scale- a scale made to rate the waves measured by another type of tool
movement magnitude scale- a tool that guesses the complete power used in a quake
Outline
Seismic waves
Detecting Seismic waves
Measuring Earthquakes
Locating the Epicenter
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